Clutch for a power train of a motor vehicle

ABSTRACT

A motor vehicle clutch has at least one flywheel  4   a  equipped with fan blades  34  at least in a zone that is radially between a hub  54  and a solid ring portion with a friction surface  52 . The clutch is configured so that the fan blades of the rotating flywheel will generate an air stream to flow over the surface portion of the flywheel on the opposite side from the friction surface for efficient cooling of the clutch.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a clutch, in particular for a powertrain of a motor vehicle. The clutch has an input shaft supporting aflywheel with a substantially ring-shaped friction surface and an outputshaft supporting a clutch disc with a friction lining conforming to thefriction surface of the flywheel. The flywheel is constrained to rotatetogether with the input shaft, and the clutch disc is constrained torotate with the output shaft. The clutch further has an axially movablepressure plate and an actuator device that serves to move the pressureplate and thereby engage and disengage the clutch. In the engagedposition, the pressure plate is urging the clutch disc intofriction-locked compressive contact against the flywheel. In thedisengaged position, the pressure plate is retracted, whereby thefriction-lock between the input shaft and the output shaft isinterrupted. The aforementioned components are enclosed in a housingwith openings for the input shaft and the output shaft to pass through.

[0002]FIG. 5 provides a general orientation of the layout and functionof a motor vehicle clutch. An input shaft 2 originating from a source ofmotive power, e.g., the crankshaft of an engine, carries a flywheel 4that is constrained on the input shaft to share its rotation. Theflywheel 4, which generally performs the function of an engine flywheel,extends as a disc from the input shaft to an outer circumference whereits contour turns into the axial direction to form a cylindrical wall,ending in a radially inward bent rim that forms an abutment ring 6.Running axially in line with the input shaft 2 is an output shaft 8. Aclutch disc 10 is attached to the output shaft through a rotationallyfixed connection. The radially outer portion of the clutch disc 10carries a substantially ring-shaped friction lining 12 designed toengage a corresponding friction surface of the flywheel 4. The flywheel4 can likewise be equipped with a friction lining.

[0003] The clutch disc 10 is axially movable in relation to the outputshaft 8, or flexibly deformable in the axial direction. A pressure discor pressure plate 14 that is axially movable in relation to the outputshaft 8 and can be rotationally constrained to the latter serves topress the clutch disc 10 against the flywheel 4. Normally, a diaphragmspring 16, seated at its outer circumference against the abutment ring6, pushes the pressure plate 14 against the clutch disc 10, so that thelatter is in non-slipping frictional engagement with the flywheel 4. Theradially inner border of the diaphragm spring is held in a retractingring 18 that is rotatably supported on an actuator ring 20. The actuatorring 20 is axially movable on the output shaft 8 by means of an actuatormechanism 22. By moving the actuator ring 20 to the right (as shown inFIG. 5) the diaphragm spring 16 is caused to change its shape so thatthe pressure plate 14 is no longer pushed against the clutch disc 10 andthe clutch is taken out of engagement. The entire arrangement isaccommodated in a housing 24 that is formed by a so-called clutch bell26 and the engine housing 28. The clutch bell 26, covering the side ofthe clutch facing towards the transmission, is attached to the enginehousing 28.

[0004] Mechanical clutches of this kind, which include one or moreflywheels, have to meet exacting requirements. The clutch is expected toengage softly, to transmit large amounts of torque, and to have a longoperational life span. If the clutch is used in conjunction withautomated shift transmissions, in particular with transmissions thatshift under load, where several gear shifts can occur in rapidsuccession under a high torque load, large amounts of heat may begenerated in the clutch, which can be detrimental to its functionalityand shorten its useful life.

OBJECT OF THE INVENTION

[0005] It is therefore the object of the present invention to furtherdevelop a clutch of the kind described above in order to increase therate at which the clutch can convert mechanical energy into thermalenergy without suffering damage.

SUMMARY OF THE INVENTION

[0006] According to the invention, the foregoing objective is met by aclutch in which the flywheel has fan blades arranged at least in a zonethat is radially inside the friction surface, so that the rotation ofthe flywheel will cause an air stream to flow over the side of theflywheel that faces away from the friction surface.

[0007] In a clutch designed in accordance with the invention, the airstream will carry the heat away significantly faster, so that even at ahigh rate of heat generation, the friction linings will remain at a lowtemperature and will therefore not be exposed to the risk of beingdamaged.

[0008] In a preferred embodiment of the invention, the flywheel, theclutch disc and the pressure plate have air passages located in a radialzone between the output shaft and the friction lining. This allows theair stream generated by the fan blades of the flywheel to flow axiallyalong the output shaft.

[0009] Also preferred according to the invention is a configuration ofthe clutch where the housing surrounds the flywheel, the clutch disc andthe pressure plate at a sufficient distance for the air to circulate ina closed loop. Passing through the aforementioned air passages in theflywheel, the clutch disc and the pressure plate, the air will move inan axial direction along the output shaft from the pressure plate to theflywheel, then turn radially outwards and continue its circulation pathbetween the housing and the flywheel, then turn into the axial directionalong the peripheral housing wall from the flywheel to the pressureplate, and finally turn back inwards in the radial direction to completethe loop of air circulation.

[0010] In another preferred embodiment of the invention, the housing hasan air inlet and an air outlet. In this case, outside air enters thehousing through the inlet, then flows on a path inside the housing thatleads through the flywheel, and leaves the housing through the airoutlet.

[0011] In the embodiment of the preceding paragraph, a preferredlocation for the air inlet is on the side of the housing that is fartheraway from the flywheel, while the air outlet is located preferably in aperipheral housing wall, so that the air flow path runs in an axialdirection from the air inlet along the output shaft, passes through theflywheel, then turns into an outward radial direction between thehousing and the flywheel and exits from the housing through the airoutlet.

[0012] In a clutch according to the invention, it is advantageous if thehousing has an interior surface that is provided with cooling fins.

[0013] In clutches according to the invention, it is preferred if theflywheel performs the function of an engine flywheel.

[0014] In preferred embodiments of the invention, it is of advantage ifthe flywheel is provided with cooling fins.

[0015] As a further advantageous concept within the scope of theinvention, a clutch may have two or more flywheels, clutch discs andpressure plates arranged in an alternating line-up along the rotationalaxis of the clutch.

[0016] In an advantageous practical embodiment of the foregoing concept,the clutch has one input shaft and two output shafts. The first outputshaft runs coaxially inside the hollow second output shaft. Theaforementioned alternating line-up, starting from the side of the inputshaft, includes:

[0017] a first flywheel rotationally fixed on the input shaft;

[0018] a first clutch disc rotationally fixed on the first output shaft;

[0019] a first pressure plate operable by means of an actuator mechanismto actuate the first clutch disc;

[0020] a second flywheel rotationally fixed on the input shaft;

[0021] a second clutch disc rotationally fixed on the second outputshaft; and

[0022] a second pressure plate operable by means of the actuatormechanism to actuate the second clutch disc.

[0023] The novel features that are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain presently preferred specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the following detailed description, examples of embodiments ofthe invention are discussed on the basis of the attached drawing inwhich

[0025]FIG. 1 represents a cross-sectional view of a first embodiment ofthe clutch according to the invention;

[0026]FIG. 2 represents a cross-sectional view of a second embodiment ofthe clutch according to the invention;

[0027]FIG. 3 represents a cross-sectional view of a flywheel;

[0028]FIG. 4 represents a perspective view of the flywheel;

[0029]FIG. 5 represents a cross-sectional view of a motor vehicleclutch.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Unlike the clutch of FIG. 5 that was discussed at the beginning,the clutches that are schematically represented in FIGS. 1 and 2 havetwo flywheels, 4 a and 4 b respectively, mounted on the input shaft 2through a rotationally locked connection. Flywheel 4 a cooperates withclutch disc 10 a, pressure plate 14 a, and diaphragm spring 16 a; whileflywheel 4 b cooperates with clutch disc 10 b, pressure plate 14 b, anddiaphragm spring 16 b. The diaphragm springs 4 a, 4 b normally push thepressure plates 14 a, 14 b against the clutch discs 10 a, 10 b, so thatthe latter are pressed into frictional engagement against the respectiveflywheels 4 a, 4 b.

[0031] The clutch disc 10 a is mounted through a rotationally lockedconnection to an output shaft 8 a, while the clutch disc 10 b is mountedthrough a rotationally locked connection to an output shaft 8 b. The twoshafts run coaxially, i.e., output shaft 8 b is hollow, and output shaft8 a extends partially inside output shaft 8 b. Clutches of this type areused, for example, with so-called power-shift transmissions, i.e.,transmissions that can be shifted while transmitting a torque betweenthe engine and the drive train, where the input shaft 2 is coupledsimultaneously or selectively to the output shafts 8 a and 8 b. Theactuator mechanism for actuating the diaphragm springs 16 a, 16 b is notshown in detail, but its principal configuration is analogous to FIG. 5.

[0032] When the transmission is shifted while transmitting torque andalso when setting the vehicle in motion from a stand-still condition, alarge amount of heat is generated between the clutch discs and theflywheels. Since the heat is not carried away efficiently by the housing24, the resultant increase in temperature is known to cause problems.

[0033] To improve the removal of heat, all of the radially orientedelements of the clutch, i.e., the flywheels, clutch discs, pressureplates and diaphragm springs are provided with passages 30 (not shown indetail) in the zone between the outside of the shafts and the innerradius of the friction linings, so that an air-flow path 32 is clearednext to the output shafts 8 a and 8 b. The flywheel 4 a is equipped withfan blades 34 and thus functions as a fan that moves air from right toleft (in FIG. 1) through the flywheel 4 a. The fan blades could also bepitched in the opposite sense, so that the air would flow from left toright, i.e., from the flywheel to the bell cover.

[0034] Between the housing 24 and the left-facing surface (in FIG. 1) ofthe fly-wheel 4 a, there is a gap in which the air can flow radiallyoutwards. The air-flow path continues left to right through the gapbetween the peripheral wall 36 of the housing 24 and a cylindrical wall38 that surrounds the clutch parts and connects the flywheels 4 a and 4b. The air flow continues radially inwards on path 40 along theright-hand end surface of the housing. Thus, the air circulates in aclosed loop around the flywheel 4 a and the cylindrical wall 38 andthereby effectively cools the flywheels 4 a and 4 b. As an effectivemeans for transferring the heat from the circulating air stream to theoutside, the interior surface of the housing is provided with coolingfins that are advantageously arranged in those areas where the exteriorsurface of the housing is exposed to the outside air.

[0035] It should be clear that the left-facing side of the flywheel 4 a(in FIG. 1) can also have cooling fins in the surface area opposite thering-shaped friction surface. The cooling fins on the flywheel 4 a canperform the additional function of a radial fan to assist in moving theair stream in the outward radial direction.

[0036]FIG. 2 illustrates a variant version of the clutch according tothe invention. Reference symbols are shown only for those elements thatdiffer from the embodiment of FIG. 1. In contrast to the substantiallyclosed housing of FIG. 1, the housing 24 of the embodiment of FIG. 2 hasan inlet opening 42 in the area of the right-facing end surface and aring-shaped outlet opening 44 along its outside circumference. Ofcourse, the inlet opening 42, also, can be substantially ring-shaped.

[0037] As is immediately evident from FIG. 2, the concept of an inlet 42and outlet 44 leads to an air-flow path 50 that does not run in a closedloop. Instead, the air enters through the inlet 42, flows leftward alongthe shafts and passes through the flywheel 4 a, from where it isdirected in the outward radial direction and expelled to the outsidethrough the outlet 44. The embodiment shown in FIG. 2 provides anespecially effective cooling of the clutch.

[0038] The flywheel 4 a is shown in cross-section in FIG. 3 and in aperspective view in FIG. 4, omitting the outer cylindrical wall 38 thatconnects the flywheel 4 a with the flywheel 4 b and ends in a radiallyinward bent rim that forms an abutment ring 6 (FIG. 5) for the diaphragmspring 16 b (FIG. 1). The cylindrical wall 38 can, for example, bebolted to the flywheel 4 a, which has fastening holes 46 provided forthis purpose on the circumference of the flywheel 4 a. As illustrated,the flywheel portion that comes into contact with the clutch disc 10 ais configured as a solid ring that carries a friction surface 52 and isjoined to a hub 54 by way of the turbine blades 34. The hub 54 has aninternal tooth profile for a rotationally fixed connection of theflywheel 4 a to the input shaft 2. The turbine blades 34 are shaped sothat the flywheel 4 a functions as an axial fan which, when the enginecrankshaft is running, propels air from right to left (in theillustrated situation) through the openings 30 between the turbineblades 34.

[0039] The invention discussed herein on the basis of the illustratedexamples can be modified in a multitude of ways. It is not necessary forthe clutch to be of a design with two output shafts. The clutch can beconfigured as shown in FIG. 5, or it can be of a multiple-disc designwhere a plurality of flywheels and clutch discs are arranged to transmittorque between the input shaft and the output shaft. For extremeheavy-duty requirements, the embodiment of FIG. 2 in particular may besupplemented by an electric fan to assist in propelling the air stream,e.g., as a temperature dependent function. It would also be possible todesign both flywheels as axial fans.

[0040] To summarize, a clutch of a kind used particularly in the powertrain of a motor vehicle has an input shaft 2 carrying one or moreflywheels 4 a, 4 b constrained to rotate together with the input shaft2. The clutch further has one or more output shafts 8 a, 8 b carryingclutch discs 10 a, 10 b constrained to rotate together with the outputshafts 8 a, 8 b, respectively. The one or more flywheels 4 a, 4 b havesubstantially ring-shaped friction surfaces facing towards correspondingfriction linings of the one or more clutch discs 10 a, 10 b. One or morepressure plates 14 a, 14 b are axially movable between an engaged and adisengaged position by means of an actuator device 18, 20, 22. In theengaged position, the pressure plate 14 a, 14 b pushes the respectiveclutch disc 10 a, 10 b into friction-locked contact against therespective flywheel 4 a, 4 b, while in the disengaged position, thepressure plate 14 a, 14 b is retracted and the friction lock between therespective clutch disc and flywheel is interrupted. The clutch furtherhas a housing 24 in which the aforementioned parts are accommodated,with openings for the input shaft and the output shaft(s) to passthrough. To provide improved cooling of the clutch, at least oneflywheel (4 a, 4 b) is configured with fan blades 34 at least in a zonethat is radially inside the friction surface, so that the rotation ofthe flywheel will generate an air stream to flow over the surfaceportion of the flywheel on the opposite side from the friction surface.

[0041] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic and specific aspects of theaforedescribed contribution to the art and, therefore, such adaptationsshould and are intended to be comprehended within the meaning and rangeof equivalence of the appended claims.

What is claimed is:
 1. A motor vehicle clutch, comprising: an inputshaft on which a flywheel with a substantially ring-shaped frictionsurface is mounted through a rotationally fixed connection; an outputshaft, on which a clutch disc with a friction lining conforming to andfacing said friction surface is mounted through a rotationally fixedconnection; an axially movable pressure plate; an actuator device thatserves to move the pressure plate between an engaged position in whichthe pressure plate is urging the clutch disc into friction-lockedcompressive contact against the flywheel and a disengaged position inwhich the pressure plate is retracted and the friction-lockedcompressive contact is interrupted; and a housing with openings for theinput shaft and the output shaft to pass through; wherein the flywheelhas fan blades arranged at least inside an inner radius of the frictionsurface, so that the rotation of the flywheel will cause an air streamto flow on the side of the flywheel that faces away from the frictionsurface.
 2. The clutch of claim 1 , wherein the flywheel, the clutchdisc and the pressure plate in a radial zone between the output shaftand the inner radius of the friction surface are equipped with airpassages allowing the air stream to flow axially along the output shaft.3. The clutch of claim 2 , wherein the housing surrounds the flywheel,the clutch disc and the pressure plate in an arrangement that provides aclosed-loop circulation path for the air stream, said path running in anaxial direction along the output shaft from the pressure plate to theflywheel, then turning radially outwards and continuing in a radialdirection between the housing and the flywheel, then turning into andcontinuing in an axial direction along a peripheral housing wall fromthe flywheel to the pressure plate, then turning into and continuing inan inward radial direction to complete the closed-loop circulation path.4. The clutch of claim 2 , wherein the housing has an air inlet and anair outlet, and an air flow path leads through the housing, said airflow path running from the air inlet through the flywheel to the airoutlet.
 5. The clutch of claim 4 , wherein the air inlet is located onthe side of the housing that is farther away from the flywheel and theair outlet is located in a peripheral housing wall, so that the air flowpath runs in an axial direction from the air inlet along the outputshaft, passes through the flywheel, then turns into and continues in anoutward radial direction between the housing and the flywheel to the airoutlet.
 6. The clutch of claim 1 , wherein the housing has an interiorsurface that is provided with cooling fins.
 7. The clutch of claim 1 ,wherein the flywheel performs the function of an engine flywheel.
 8. Theclutch of claim 1 , wherein the flywheel is provided with cooling fins.9. The clutch of claim 1 , comprising a plurality of axially stackedfunctional groups, each of the functional groups having a flywheel, aclutch disc and a pressure plate.
 10. The clutch of claim 9 , comprisinga first output shaft and a second output shaft, wherein the secondoutput shaft is hollow and the first output shaft runs coaxially insidethe second output shaft; and further comprising in an axially sequentialarrangement from the input shaft to the first and second output shafts:a first flywheel rotationally fixed on the input shaft; a first clutchdisc rotationally fixed on the first output shaft; a first pressureplate operable by means of an actuator mechanism to actuate the firstclutch disc; a second flywheel rotationally fixed on the input shaft; asecond clutch disc rotationally fixed on the second output shaft; and asecond pressure plate operable by means of the actuator mechanism toactuate the second clutch disc.